The present invention generally relates to the field of gear design, and more particularly relates to gear systems which are self-locking and non-backdrivable.
An example of prior art gear systems which are self-locking and non-backdrivable include harmonic gear assemblies which employ flexible metal bands or flexible metal cups that have gear teeth machined into their outer periphery. These bands or cups are forcibly deformed with inner oval cams that employ many pins or balls or bearings, against fixed ring type spur gears. These configurations allow for the smooth movement of the flex cup or flex band, while only engaging several teeth at a minimum of one position, but usually two or three positions. The bi-lobular or tri-lobular cams are rotated one full revolution which only engages a small number of teeth in the fixed outer ring gear. This creates a gear ratio relative motion, while locking the band or cup to the fixed outer ring gear.
Other prior art embodiments utilize two ring gears with different numbers of teeth at different pitch diameters, or different tooth sizes at the same pitch diameter. This embodiment employs an internal gear set with two sets of spur gear planets that share the same set of pivot shafts. By fixedly attaching two different sized gears on the same set of shafts, or two same sized gears with different numbers of teeth on the same set of shafts, these assemblies can be rotated within a side-by-side ring gear pair and yield a gear ratio. Two gears on the same shaft with different pitch diameters or different numbers of teeth are difficult to manufacture in one piece, and unnecessarily complex as a pair of pinned or bolted or welded gears. Separate gears fixed together are not as robust as a continuous metal cross section.
Thus, while self-locking or non-backdrivable gearing concepts have been proposed in the past, these prior art designs are typically complex, costly to produce and/or composed of components that are not robust and/or redundant. Additionally, these prior designs are unnecessarily complex and made up of many pins, balls, bearings, bands, and fasteners.